1. Field of the Invention
The present invention relates to an apparatus and method for processing an information signal. More particularly, it relates to an apparatus and a method each for processing an information signal in which a plurality of processing pieces on an information signal are sequentially performed.
2. Description of Related Art
An upgraded structure employing a processing portion (e.g., substrate, chip, or device) as a unit is capable of greatly changing an operation condition as a new processing portion replaces the existing one or is added thereto. For example, it may be considered that an apparatus for processing an image signal is realized by using this upgraded structure. In this case, it may be desired to change processing contents to be performed by a predetermined one of processing portions that constitute the apparatus for processing the image signal, for a predetermined unit, for example, for each frame. For example, in a case where the predetermined processing portion performs Picture-in-Picture-screen-processing, it is necessary to change a position where a Picture-in-Picture screen is displayed, for each frame. In this case, it is necessary to supply a control command to this predetermined processing portion in synchronization with a frame of an image signal which is input to this predetermined processing portion.
Japanese Patent Application Publication No. H07-28642 discloses a pipeline computing unit in which n number of stages of computing units are used to perform operations on input data according to a pipeline system (see FIGS. 1 and 3-5 of the above publication). In this pipeline computing unit, contents of processing to be performed by the n number of stages of computing units are changed on the basis of a reference signal such as a frame pulse synchronized with the input data. In this case, as it goes through the n number of stages of computing units to the latter ones, the processing data is delayed more, so that a timing for changing the processing contents by each of the computing units, that is, a timing for supplying the control command (instruction or coefficient) is adjusted by using a delay unit so that proper operational results may be obtained even after alteration of the processing contents.
In the pipeline computing unit described in the above publication, the timing for supplying the control command to each stage of the computing unit is adjusted by using a delay unit. Such a system is simple and preferable if operations are fixed as with the pipeline computing unit described in this publication. However, in the above apparatus for processing the image signal that has such an upgraded structure, each time a new processing portion replaces the existing one or is added thereto, it is necessary to, for example, readjust a timing for supplying the control command to the above predetermined processing portion. Thus, it is difficult to apply such the system to the upgraded-structure apparatus.
It is an object of the present invention to provide an apparatus and method for processing an information signal, in which a plurality of processing portions processes the information signal sequentially, thereby easily realizing alternation of the processing to be performed by a predetermined one of the processing portions for each predetermined unit.